1. Field of the Invention
The present invention relates to a system and method for controlling temperature for an exhaust gas oxygen sensor used with a variable displacement engine.
2. Background Art
Fuel economy for a multi-cylinder internal combustion engine can be improved by deactivating some of the engine cylinders under certain operating conditions. Reducing the number of operating cylinders reduces the effective displacement of the engine such that it is sometimes referred to as a variable displacement engine. Depending upon the particular configuration of the variable displacement engine, one or more cylinders may be selectively deactivated to improve fuel economy under light load conditions, for example. In some engine configurations, a group of cylinders, which may be an entire bank of cylinders, is selectively deactivated.
Reducing the number of operating cylinders may also reduce the operating temperature of various engine and/or vehicle components which may adversely affect desired engine operation. For example, exhaust gas oxygen sensors used in conjunction with emission control devices, such as catalytic converters, require a minimum operating temperature to provide a reliable signal which may be used for more efficient closed loop control of the air/fuel ratio. For variable displacement engines configured to selectively operate an entire bank of cylinders, sensors associated with the deactivated bank may cool below the desired operating temperature.
An object of the present invention is to provide a system and method for controlling temperature of an exhaust gas oxygen sensor used with a variable displacement internal combustion engine to maintain a desired operating temperature, particularly for bank-configured engines.
In carrying out the above object and other objects, advantages, and features of the invention, a system and method for controlling temperature of an exhaust gas oxygen sensor in a system having a variable displacement engine include monitoring temperature of the sensor, comparing the sensor temperature to a corresponding desired temperature, and controlling the system to maintain the sensor temperature at or above the desired operating temperature. In one embodiment, the sensor is a heated exhaust gas oxygen (HEGO) sensor and the method includes controlling an integrated sensor heater to maintain the sensor temperature above the desired operating temperature. Depending upon the particular application, the system may also be controlled by controlling the engine to reactivate at least one deactivated cylinder to increase the temperature of the sensor alone or in combination with controlling an integrated or auxiliary sensor heater for systems using HEGO sensor(s).
The present invention provides a number of advantages. For example, the present invention controls the engine and/or the sensor heater to maintain a minimum desired operating temperature to facilitate closed loop control of the air/fuel ratio which generally reduces feedgas emissions and provides more efficient operation of the engine and/or associate d emission control devices.